1. Technical Field of the Invention
This invention relates to a fluid compressor, and more particularly to a motor driven fluid compressor having compression and drive mechanisms within a hermetically sealed housing.
2. Description of the Prior Art
Motor driven fluid compressors having compression and drive mechanisms within a hermetically sealed housing are known in the art. For example, as shown in FIG. 1, Japanese Patent Application Publication No. 2-215982 discloses a motor driven fluid compressor 200 having an outer housing 200'. The compression mechanism includes a fixed scroll 201 having first circular end plate 221a and first spiral element 221b extending downwardly from a lower end surface of first circular end plate 221a. Outer peripheral wall 230, extending downwardly from a peripheral portion of one end surface of first circular end plate 221a, is connected to first inner block 215. The compression mechanism further includes orbiting scroll 202 disposed between fixed scroll 201 and first inner block 215. Orbiting scroll 202 includes second circular end plate 222a and second spiral element 222b extending upwardly from an upper end surface of second circular end plate 222a. The first and second spiral elements 221b, 222b interfit with a radial and angular offset.
The drive mechanism includes drive shaft 211 and motor 232 for driving drive shaft 211. Drive shaft 211 includes an integral pin member 234 extending upwardly from a top end thereof. Pin member 234 is drivingly connected to orbiting scroll 202. A rotation preventing mechanism (not shown) is disposed between orbiting scroll 202 and first inner block 215 so that orbiting scroll 202 orbits, but does not rotate, during rotation of drive shaft 211. A lower end surface of second circular end plate 222a radially slides on an upper end surface of first inner block 215 during orbital motion of orbiting scroll 202. Second inner block 216, disposed below first inner block 215, includes central bore 236 through which drive shaft 211 passes. An upper end portion of drive shaft 211 is rotatably supported by second inner block 216 by a bearing (not shown) which is disposed within central bore 236. Inlet pipe 203, which is hermetically connected to side wall 238 of housing 200' at a portion below second inner block 216, conducts the refrigerant gas from one external element of a cooling circuit, such as an evaporator (not shown), to inner space 239 of housing 200'.
Valved discharge port 207 is axially formed through a central portion of first circular plate 221a of the fixed scroll 201. Outlet pipe 208, which hermetically penetrates through a top end of housing 200', is connected to valved discharge port 207 at its inner end so as to conduct the discharged refrigerant gas to another external element of the cooling circuit, such as a condenser (not shown). Axial channel 214 is formed between one peripheral end of the first and second inner blocks 215 and 216 and inner wall 240 of housing 200'.
While, on the one hand, it is be desirable to reduce the outside diameter of the compressor so that it occupies less space within the engine compartment, this has the incidental effect of reducing the capacity of the compressor, as the outside diameter of the scroll members are also reduced. Therefore, a trade off is typically achieved between maintaining a suitable compression ratio and reducing the outside diameter of the compressor housing. The problem of reducing the outside diameter of a compressor such as that shown in FIG. 1 is complicated because axial channel 214, which supplies refrigerant to the suction side of the compressor, runs along inner wall 240 of housing 200'. Consequently, if the outer diameter of compressor 200 is reduced, axial channel 214 might be choked such that insufficient refrigerant is supplied to the suction side of the compressor.
Moreover, in addition to reducing the outer diameter of the compressor while maintaining its capacity, it is desirable, if a lighter compressor unit is required, to reduce the number of parts. For example, with reference to FIG. 2, there is shown a prior art compressor disclosed in U.S. Pat. No. 4,936,756. As with the compressor of FIG. 1, there is disclosed a motor driven fluid compressor 200". The compression mechanism includes fixed scroll 201' having first circular end plate 221a' and first spiral element 221b' extending from an end surface of first circular end plate 221a'. The compression mechanism further includes orbiting scroll 202' comprising second circular end plate 222a' and second spiral element 222b' extending from an end surface of second circular end plate 222a'. The first and second spiral elements 221b', 222b' interfit with a radial and angular offset.
The drive mechanism includes drive shaft 211' driven by motor 232'. Drive shaft 211' includes an integral pin member 234' extending from an inner end thereof. Pin member 234' is drivingly connected to orbiting scroll 202'. Rotation preventing mechanism 260' is provided so that orbiting scroll 202' orbits, but does not rotate, during rotation of drive shaft 211'. Inlet pipe 203', which is hermetically connected to a side wall 238' of housing 200'", conducts the refrigerant gas from one external element of a cooling circuit, such as an evaporator (not shown), to inner space 239' of housing 200'".
At one end, drive shaft 211' is supported by inner block 271' through bearings 270', and at its other end, drive shaft 211' is supported by inner block 273' through bearings 272'. Moreover, stator 274' is supported at one end by inner block 271' and at the other end by inner block 273'. In order to reduce the weight of the compressor, the number of parts could be reduced. For example, while it might be desirable to remove inner block 273' from the compressor of FIG. 2, the stator and drive shaft would consequently be cantilevered from the sole remaining inner block 271'. Thus, if parts such as inner block 273' are to be removed from the compressor, the function of the parts so removed must be preformed by the remaining elements of the compressor.